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Chapter 7.2

Chapter 7.2. 1. Continuing: Factors affecting intensity of SQA activities Verification, validation and qualification Development and quality plans for small and for internal projects A model for SQA defect removal effectiveness and cost. Chapter 7.2. 2.

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Chapter 7.2

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  1. Chapter 7.2 1

  2. Continuing: • Factors affecting intensity of SQA activities • Verification, validation and qualification • Development and quality plans for small and for internal projects • A model for SQA defect removal effectiveness and cost Chapter 7.2 2 Integrating quality activities in the project life cycle

  3. SQA Activities are linked to the completion of a project phase Requirements, design, etc. The SQA activities need to be integrated into the development plan that implements one or more software development models, such as the waterfall, prototyping, spiral, … They need to be activities just like other more traditional activities – be entered in plan, scheduled, etc. Factors affecting Intensity of SQA Activities 3

  4. SQA planners need to determine A list of SQA activities needed for the project And then for each activity, they need to decide on Timing Type of QA activity to be applied (there are several) Who performs the activity and resources required. Important to note that many participate in SQA activities Development team Department staff members Independent bodies Resources required for the removal of defects and introduction of changes. Factors affecting Intensity of SQA Activities 4

  5. Sad testimony that few want to allocate the necessary time for SQA activities. This means time for SQA activities and then time for subsequent removal of defects. Often, there is no time for follow-on work!! Activities are not simply cranked in and absorbed! So, time for SQA activities and defect correction actions needs to be examined. Factors affecting Intensity of SQA Activities 5

  6. Project Factors Magnitude of the project – how big is it? Technical complexity and difficulty Discuss Extent of reusable software components – a real factor Severity of failure outcomes if project fails – essential! Team Factors Professional qualifications of the team members Team acquaintance w/ project and experience in the area Availability of staff members who can professionally support the team, and Percentage of new staff members in the team. Factors Affecting the Required Intensity of QA Activity 6

  7. Recognize that these activities take days to undertake, and days to correct. Here are some sample activities: (and don’t forget the planning for the reviews, materials, …) Design Review of Requirements Design Review of xxxxx Design Review of …. Inspections of …. Inspections of ….. Unit Testing of software code for each interface module … Unit testing of …. System Testing of …. Design Review of User’s Manual….. So, what are the activities?? 7

  8. Verification, Validation, and Qualification 8 Three aspects of Quality Assurance for Software Products: Verification – The process of evaluating a system or component to determine whether the products of a given development phase satisfy the conditions imposed at the start of that phase Validation - The process of evaluating a system or component during or at the end of the development process to determine whether it satisfies specified requirements Qualification - The process used to determine whether a system or component is suitable for operational use IEEE Std 610.12-1990 (IEEE 1990)

  9. Verification looks at the consistency of the products being developed with products developed in previous phases. Developers verify as we go. Validation is a customer thing – customers validate the outputs, etc. Validate against their original requirements. Necessary for customersatisfaction. Qualification focuses on operational aspects – maintenance is the main issue. Has development taken place IAW professional standards and procedures such that follow-on maintenance is easier to undertake? Planners need to determine which of all these need to be examined in each QA activity. More on VV and Q 9

  10. 10 Model for SQA defect removal effectiveness and cost for defect detection and removal • The model addresses two quantitative aspects of the SQA planning addressing several defect detection activities. • Want to study the SQA plan’stotal effectiveness in removing project defects, and • The total costsof removal of project defects • Note again that SQA activities must be integrated within the project’s development plan.

  11. The data: Model based on three types of data: Defect origin distribution in which phase did the defects occur Defect removal effectiveness, and how effective are we at removal of defects? Cost of defect removal. how much does it cost per defect per phase!!! Model for Defect Removal 11

  12. Very consistent over many years: Distribution of Defects: Requirements Specs 15% Design 35% Coding / integration 40% Documentation 10% Defect Origin Distribution 12

  13. Generally speaking, the percentage of removed defects is lower than the percentage of detected defects, because some corrections are ineffective or inadequate. We simply miss some!! Others are undetected and uncorrected and passed on to successive development phases. Lingering defects coupled with introduced defects in current development phase add up!!! For discussion purposes, we will assume the filteringeffectiveness of accumulated defects of each quality assurance activity is not less than 40%, that is, each activity removes at least 40% of the incoming defects. Defect Removal Effectiveness 13

  14. Removal effectiveness QA ActivityAverage defect filtering effectiveness rate requirements specs review 50% design inspection 60% design review 50% code inspections 65% unit test 50% Unit test > code review 30% integration test 50% system tests / acceptance 50% documentation review 50% Defect Removal Effectiveness 14

  15. Removal of defects differs very significantly by development phase. Cost are MUCH greater in later development phases. Note: In general, defect removal data is not commonly available. Most agree with the data based on key studies. (next slide) Cost Removal 15

  16. Defect removal phase Defect removal effectiveness Average relative defect removal cost {cost unit} Defect origination phase Req Des Uni Int Doc Requirement specification (Req) 50% 1 --- --- --- --- Design (Des) 50% 2.5 1 --- --- --- Unit coding (Uni) 50% 6.5 2.6 1 --- --- Integration (Int) System documentation (Doc) 50% 50% 16 16 6.4 6.4 2.5 2.5 1 1 System testing / Acceptance testing (Sys) 50% 40 16 6.2 2.5 1 Opertion by customer (after release) 100% 110 44 17 6.9 2.5 16 Defects removal effectiveness for quality assurance plans

  17. Our Model is based on following assumptions: Development process is linear, sequential following waterfall model There is a number of new defects introduced each phase Review and test software quality assurance activities serve as filters, removing a percentage of defects and letting the rest pass to next development phase as we saw three slides back. At each phase, incoming defects are the sum of those not removed plus new defects in current phase Cost of defect removal is calculated for each SQA activity by multiplying the number of defects removed by the relative cost of removing a defect. (see table, previous slide) Remaining defects are passed to the customer. (this is the heaviest cost for defect removal) The Model 17

  18. The models we show use these parameters: POD – Phase originated defects PD – Passed defects (from former phases) %FE - % of filtering effectiveness RD – Removed defects CDR – Cost of defect removal TRC – Total Removal Costs Model - parameters 18

  19. This model applies a standard quality assurance plan (standard defects filtering system) composed of QA activities, that is, ‘filters’ we have: QA activity removal effectiveness Cost of removing defect Requirements Spec review 50% 1 Design Review 50% 2.5 Unit Test 50% 6.5 Integration tests 50% 16 Documentation Review 50% 16 System Test 50% 40 Operation Phase 100% 110 First Model (standard) 19

  20. Using the standard quality assurance plan’s quality assurance activities on previous slide, a process-oriented illustration of the standard QA plan model follows: 20

  21. 21 POD – phase originated defects PD – passed defects %FE – percent filtering RD – removed defects CDR - Cost of removing defects TRC - Total Cost of Defect Removal

  22. But we can do better using a comprehensive quality assurance plan with more activities, and hence better filtering. The comprehensive quality assurance plan (comprehensive defects filtering system) accomplishes the following: 1. Adds two quality assurance activities so that the two are performed in the design phase as well as in the coding phase We have a Design Inspection and a Design Review vice Design, and Code Inspections and unit test vice simple Unit Test 2. Improves the ‘filtering’ effectiveness of other quality assurance activities. Costs of Defect Removal 22

  23. 23 Design Inspect and Design Review 12.3 and 4.9 Code inspection precedes unit test 10.5 and 6.3 Comprehensive Quality Assurance Plan: POD – phase originated defects PD – passed defects %FE – percent filtering RD – removed defects CDR - Cost of removing defects TRC - Total Cost of Defect Removal 6.5 6.6 2.6

  24. Conclusions: The standard plan successfully removes 57.6% of the defects in requirements and design compared to 90.2% in the comprehensive plan before coding begins. Results from more intensive defect-removal efforts. The comprehensive plan as a whole is much more economical than the standard plan as it saves 41% of the total resources investing in defect removal, compared with the standard plan Compared to the standard plan, the comprehensive plan makes a greater contribution to customer satisfaction by drastically reducing the rate of defects detected during regular operations: 6.9% to 2.6% Comprehensive Plan 24

  25. So, in general, the quantitative results of the comparison comply nicely with the SQA approach. Additional investments in QA activities yield substantial savings in defect removal costs. Conclusion 25

  26. Individually, you are to answer the following questions and send them to me via Blackboard Assignment. Questions: 7.6 and 7.7 Homework 26

  27. Team 3: Here are your primary questions: These are the ones for you to provide for class discussion with your team being the primary participants Questions: 7.2, 7.5, 7.4 Discussion Forum 27

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